1) Field of the Invention
The subject invention relates to a formulated resin component for use in a spray-in-place foam system to produce a low density polyurethane foam. More particularly, the subject invention relates to low density open-celled polyurethane foams for use as an insulation material in structures, such as buildings.
2) Description of Related Art
Various formulated resin components are used in polyurethane spraying systems to produce polyurethane foams. Some formulated resin components are shown generally in U.S. Pat. Nos. 5,859,082 and 3,094,434. These resin components typically include a blowing agent, additives, and a polyol blend of various constituents. The resin component is sprayed with an isocyanate component to form the polyurethane foam. During spraying, the resin component reacts with the isocyanate component. The resin component and the isocyanate component are sprayed at a volumetric ratio of 1 to 1 using typical spraying equipment. One type of spraying equipment capable of use with a two component system is shown in U.S. Pat. No. 6,527,203. One problem encountered in spray foam systems is dripping of the polyurethane foam while it is curing. The extent of dripping of the polyurethane foam may be increased and decreased by modifying the volumetric ratio of the resin component to the isocyanate component. Further, dripping can be controlled by adding additional constituents to the resin component. Most related art systems spray the components at the 1:1 volumetric ratio and add additional constituents. One reason for spraying at a 1:1 volumetric ratio is that the supplies of the resin component and the isocyanate component are consumed at an equal rate and makes order replenishment easy. Another reason is because inexpensive spraying equipment is available to deliver the components at the same volumetric rate. However, spraying at a 1:1 ratio does not always produce adequate physical properties and results in too much dripping.
One example of a polyurethane foam formed from a spray foam system is shown in U.S. Pat. No. 5,449,699. The polyurethane foam includes a polyol component that is amine-initiated and has a tertiary amine catalyst. The polyol component is reacted with an isocyanate component in a weight ratio of 0.9:1 to 1.3:1. However, the polyurethane foam of the '699 patent is a closed-cell polyurethane foam that has a density of greater than 1.5 pound per cubic foot (pcf).
Another example of a polyurethane foam is described in U.S. Pat. No. 4,260,514. The '514 patent discloses a polyurethane foam formed from a brominated diol, other halogen compounds, and three polyols. These halogen compounds are known to those skilled in the art to act as flame retardants. One of the polyols includes an oxyalkylated polyamine present in an amount of from about 4 to about 20 weight percent. These polyols are reacted with an isocyanate to produce the foam having a flame spread characteristic of less than 25. However, the polyurethane foam has a density of greater than 1.5 pcf and uses freon as the blowing agent. The '514 patent does not disclose or suggest forming the polyurethane foam having a density of less than 1 pcf and with water as the blowing agent. The use of freon requires additional equipment, such as pressurized vessels to deliver the constituents and typically results in foams having a density of greater than 1 pcf. Changing blowing agents between water and freon greatly impacts the physical properties of the resultant foam and results in different densities.
In sum, the polyurethane foams formed from the spray foam systems of the related art are characterized by one or more inadequacies. Therefore, it is desirable to provide a formulated resin component for use in a polyurethane spray foam system to produce a polyurethane foam that has a low density and that has improved physical characteristics, such as flame spread characteristics, water absorption, and water vapor permeance.